本篇論文主要是探討秀麗隱桿線蟲的覓食行為和趨光性的研究。線蟲一般是生活在低溫下的土壤中，藉由吃微生物來維持生命。線蟲有1031個細胞，當中有300個是神經細胞，因為線蟲的細胞已經被定序了，在很多的研究方面來說是一個理想的樣本生物。
為了要維持生命，覓食和尋找食物對生物來說是一個很基本的能力。然而，食物不會均勻地分布在環境當中。即使線蟲有神經來辨別它們所生存的環境和簡單的神經網絡來進行決策，了解這種理想的樣本生物的覓食行為代表了簡單生物搜尋模式的縮影。實驗上，我們在空間上設計了食物的圖案，讓線蟲尋找食物。在覓食的過程中，我們記錄其運動來定義覓食的狀態，並觀察其行為上有甚麼樣的變化。我們用頭擺動的角度來定義其覓食的狀態。線蟲爬行的動作造成的較低的爬行頻率表示其移動速度。另外，還注意到線蟲的頭有探測的動作。我們將頭部的探測動作造成的較高的搜尋頻率定義為覓食狀態的重要指標。我們發現當線蟲接近食物的時候，其頭部擺動的次數增加和速度下降，表示線蟲需要更高的採樣率來修正自己的軌跡朝著食物的方向前進。我們還使用化學引誘劑和突變株來證明我們的模型。
此外，線蟲一般是生活在土讓裡面，我們認為它不具有感光的器官。有感光功能的生物都被觀察到有感光性的行為。然而，當我們照光在線蟲身上的時候，發現它有避光的現象。因此，我們分析線蟲的運動來了解其感光性的行為。

The aim of this thesis is to investigate the foraging and phototaxis behavior of Caenorhabditis elegans. C. elegans is a free-living nematode about 1 mm in length and lives in the soil environment at low temperature by eating microorganism to survive. C. elegans is the ideal model organism in many field of research because of their well-studied fate of its 1031 cells including ~ 300 neuron cells.
Searching for food, foraging, is the fundamental skill for living organism to survive. However, food is not homogenous distributed in the natural environments. Even C. elegans has nerves to identify their surroundings and simple neuron network for decision making, understanding the foraging behavior of this model organism C. elegans represents the epitome of a searching mode of this simple living creature. We design spatial food patterns for C. elegans to search. During the foraging process, we record images of their locomotion to define the foraging states and reveal the pattern changing of foraging behavior. We use the head angle represents the foraging states. The low creeping frequency from the crawling motion indicates the moving speed. We notice there is another head exploring motion. We defined a searching frequency from the head exploring motion as an important indicator of foraging states. We found that the numbers of head swing increase and velocity decreases when C. elegans approaching the food indicating the worm needs higher sampling rate to find the correction direction of motion toward the food. We also use chemical attractant and mutant strains to test our model.
Besides, C. elegans is regarded as having no light-sensing organism because of living in the soil environment. The phototaxis behavior is observed in living creatures having photoreceptor organism. However, we found C. elegans has negative phototaxis behavior when we illuminated the light on it. Therefore, we analyzed the locomotion of C. elegans to discover the phototaxis behavior.

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